Apparatus for controlling the tension on web material

ABSTRACT

Web material is unwound from a roll and supplied to a web unwind unit having a tension sensing mechanism mechanically connected thereto. The web material having a desired tension is drawn by an envelope machine drive at a first preselected linear speed through the web unwind unit into abutting contact with the tension sensing mechanism. The tension sensing mechanism includes a tension sensing roll arranged for rotation with an eccentrically supported shaft by a pair of tension arms. The tension sensing roll is arranged to apply a preselected pressure upon the web material so that the tension sensing roll responds to an increase in web tension by rotating with the tension arms in clockwise direction about the eccentrically supported shaft. The eccentrically supported shaft revolves in clockwise direction to move a pressure roll rotatably supported thereon toward a feed roll urging the web material into frictional engagement therebetween. The web material is fed by the pressure roll and the feed roll at an increased preselected linear speed to decrease the web tension. The tension sensing roll responds to a decrease in tension by rotating in counterclockwise direction with the tension arms. The eccentrically supported shaft also revolves in counterclockwise direction to release the web material from frictional engagement between the feed roll and the pressure roll restoring the web material to the slower preselected linear speed as provided by the envelope machine drive.

[11] 3,826,442 July 30, 1974 APPARATUS FOR CONTROLLING THE TENSION ON WEB MATERIAL [75] Inventor: Erwin Bethke, Erkelenz-Keyenberg,

Germany [73] Assignee: F. L. Smithe Machine Company,

Inc., Duncansville, Pa.

[22] Filed: Jan. 30, I973 [2]] Appl. No.: 328,134

[52] US. Cl. 242/755 [51] Int. Cl. B65h 25/04 [58] Field of Search 242/7541, 75.42, 75, 75.1,

Primary Examiner-John W. Huckert Assistant Examiner-Edward J. McCarthy Attorney, Agent, or Firm-Stanley J. Price, Jr.

[57] ABSTRACT Web material is unwound from a roll and supplied to a web unwind unit having a tension sensing mechanism mechanically connected thereto. The web mate rial having a desired tension is drawn by an envelope machine drive at a first preselected linear speed through the web unwind unit into abutting contact with the tension sensing mechanism. The tension sensing mechanism includes a tension sensing roll arranged for rotation with an eccentrically supported shaft by a pair of tension arms. The tension sensing I roll is arranged to apply a preselected pressure upon the web material so that the tension sensing roll responds to an increase in web tension by rotating with the tension arms in clockwise direction about the eccentrically supported shaft. The eccentrically supported shaft revolves in clockwise direction to move a pressure roll rotatably supported thereon toward a feed roll urging the web material into frictional engagement therebetween. The web material is fed by the pressure roll and the feed roll at an increased preselected linear speed to decrease the web tension. The tension sensing roll responds to a decrease in tension by rotating in counterclockwise direction with the tension arms. The eccentrically supported shaft also revolves in counterclockwise direction to release the web material from frictional engagement between the feed roll and the pressure roll restoring the web material to the slower preselected linear speed as provided by the envelope machine drive.

11 Claims, 4 Drawing Figures APPARATUS FOR CONTROLLING THE TENSION ON WEB MATERIAL BACKGROUND OF THE INVENTION 1 1. Field of the Invention This invention relates to apparatus for controlling the tension of web material and more particularly to apparatus for maintaining a preselected tension on 'web material suitable for use in an envelope machine.

2. Description of the Prior Art The manufacture of envelopes from a continuous web and operations in other areas where it is necessary to continuously feed paper or other web material from a revolving reel requires uniform tension throughout the unwinding process to remove slack in the material associated with a lack of tension or prevent breakage of material resulting from excessive tension. Devices for controlling the tension of the web by monitoring the feed rate of the web are well known in the art.

U.S. Pat. No. 3,386,635 describes a web tensioning method and apparatus for applying tension to a moving web of sheet material. A movable shoe is held in contact with the moving web material by fluid applied at a pressure sufficient to remove web flutter attributed to a decrease in web tension. Fluid pressure is applied to the shoe so that the surface thereof, in contact with the web, exerts pressure on the web. Sufficient fluid pressure is maintained to eliminate flutter in the unsupported section of the web material across the shoe. A shoe mounting means is provided to permit movement of the shoe towards and away from the moving web so that the shoe may exert a variable pressure on the web for removing local looseness in the web.

British Pat. No. 1,272,817 discloses a web tension control system for use with a web unwind stand having a tension sensing roll engaged with an unwinding web of a mill roll. The tension sensing roll actuates pneumatic brakes through suitable gearing to apply braking torque to the shaft supporting the mill roll. The tension sensing roll operably actuates an air regulator to supply air to the pneumatic brakes which apply the torque and thereby control the tension of the web material unwinding from the mill roll.

U.S. Pat. No. 3,385,535 provides a web take-up reel controller that includes a take-up reel responsive to the tension of the web. The take-up reel continuously winds the web until the tension becomes too great and deflects an arm to disengage the drive and stop the rotation of the reel. A dancer arm responsive to changes in the tape tension is provided toeffect engagement and release of a spring clutch drive means drivingly connected to the take-up reel. Whenever the input tape drags across the take-up reel or is stopped, the spring clutch drive means will terminate the unwinding process and automatically restart the process when sufficient slack is restored in the tape. There is need for apparatus which is sensitive to variations which occur in tension on web material and capable of instantaneously responding to such variations by increasing or decreasing web tension to the desired level.

SUMMARY OF THE INVENTION ln accordance with the present invention there is provided apparatus for controlling the tension on web material which includes a roll of web material rotatably supported to permit continuous unwinding of the web material from the roll. The web material is supplied from the roll to an unwind unit which includes a feed roll and a pressure roll. At least one of the rolls is driven at a preselected linear speed to intermittently feed the web material frictionally engaged between the feed roll and the pressure roll to a machine for further processing the web material, such as an envelope forming machine. A tension sensing mechanism positioned adjacent the unwind unit is arranged in abutting relation with the web material whereby the web material exerts a continuously opposing force upon the tension sensing mechanism. The pressure roll is mechanically connected to the tension sensing mechanism for moving the pressure roll toward and away from the feed roll to frictionally engage the web material therebetween so that the web material is fed at a higher linear speed to the envelope machine. Thus, a uniform tension is maintained in a segment of the web material between the unwind unit and the envelope machine.

The tension sensing mechanism includes a tension sensing roll rotatably supported on a shaft which is suitably connected at one end between a pair of tension arms. The tension arms are connected at the other end for rotation with a shaft eccentrically supported in a pair of bushings for rotation relative thereto. The pressure roll is rotatably supported on the eccentrically supported shaft by a pair of bearings. The tension sensing roll is operably arranged to maintain a preselected force upon the web material. Therefore, a variation in the applied force associated with an increase or decrease in the web tension will actuate the tension arms and the tension sensing roll to rotate on the eccentrically supported shaft to thereby maintain the preselected pressure upon the web material.

When the tension on the segment of the web material between the unwind unit and the envelope machine increases from the desired tension, the tension sensing roll and tension arms rotate in clockwise direction about the eccentrically supported shaft. Clockwise rotation imparted to the eccentrically supported shaft moves the pressure roll toward the feed roll to frictionally engage the web material therebetween. Because the speed of the feed roll is higher than the speed of the envelope machine drive, the unwind unit supplies web material to the envelope machine faster than it is capable of receiving the web material resulting in a decrease in the web tension on the segment between the unwind unit and the envelope machine.

When too much slack develops in the web material, the accompanying decrease in web tension actuates the tension sensing roll and tension arms to rotate in counterclockwise direction on the eccentrically supported shaft. counterclockwise rotation of the eccentrically supported shaft moves the pressure roll supported thereon away from the feed roll and out of frictional engagement with the web material. Thus, the unwind unit no longer feeds web material to the machine at the higher linear speed. The web material is drawn by the envelope machine drive at a lower linear speed to increase the web tension. With this arrangement the tension sensing roll constantly oscillates about the eccentrically supported shaft to maintain a uniform tension on the web material.

Accordingly, the principal object of this invention is to provide apparatus for controlling tension on web material by constantly sensing the tension on the web material and thereby increase or decrease the tension to maintain a desired tension on the web material.

Another object of this invention is to maintain a uniform tension on web material drawn into an envelope forming machine or a printing press for the completion of further operations.

Still another object of this invention is to provide a web tension control apparatus that continuously responds to variations in tension on web material and increases the feed rate to a machine in order to adjust the web tension to the desired level.

These and other objects of this invention will be more completely disclosed and described in the following specification, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation of the apparatus for controlling the tension on web material.

FIG. 2 is a top plan fragmentary view illustrating the tension control apparatus according to the invention.

FIG. 3 is a diagrammatic view illustrating the relative positions of the feed roll and pressure roll for decreasing the web tension according to the invention.

FIG. 4 is a diagrammatic view illustrating the relative positions of the feed roll and pressure roll for increasing the web tension according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT from a web. The envelope machine is not shown, and

only those parts of the envelope machine which are essential for a complete understanding of the invention are diagrammatically illustrated in FIG. 1.

The web tension control apparatus 10 includes a web supply unit 12 and a web unwind unit 14 having a tension sensing mechanism 15 connected thereto. The web supply unit 12 comprises a rearwardly extending portion 16 of the machine support frame 18. The rearwardly extending portion 16 has an annular recess 20 arranged to receive a roll of web material 24 mounted on a web roll shaft 26.

The web material 28 is unwound from the roll 24 in the direction indicated by the arrow and extends around an idler roll 30 which is rotatably supported to one end of idler arm 32 that is maintained in frictional engagement with the roll 24. The web material 28 passing around the idler roll 30 is directed over the idler roll 34 rotatably secured to the other end of the idler arm 32. The web material 28 is fed over the idler roll 34 and directed therefrom into abutting relation with the idler roll 36 rotatably mounted to one end of link 38. The other end of link 38 is connected for rotation with the idler roll 34 which, in turn, links the idler arm 32 to the link 38. A support shaft 39 is secured at one end to idler roll 36 and at the other end is connected to a cylindrical counterweight 40.

As the roll 24 unwinds and grows smaller, the counterweight 40 acts to transmit a downwardly exerting force upon the idler arm 32 and thereby maintain the arm 32 in frictional engagement with the roll 24. By applying a' continuously downwardly exerting force upon the roll 24, the idler arm 32 retards the roll 24 peripheral velocity which increases as the roll 24 unwinds. With this arrangement, the roll 24 is arranged to continuously supply web material 28 to the pairs of overlying pressure rolls 25, as illustrated in FIG. 1, of the envelope machine for further processing. Although the web supply unit 12 is illustrated, it is not essential to the invention for maintaining the tension on the web 28 uniform.

The web material 28 passing around pick-up roll 42 advances upwardly into contact with a wraparound roll 44 and therefrom through the nip 49 formed between a pressure roll 46 and the feed roll 48. The web material 28 in abutting relation with the feed roll 48 passes through the nip 49 and follows a substantially vertical path upwardly into contact with the tension sensing roll 50 of the tension sensing mechanism 15. Thereafter, the web material 28 is fed between the overlying pressure rolls 25 which are arranged to rotate and convey the web material 28 toward the envelope machine at preselected linear velocity.

Referring to FIG. 2, there is illustrated the pressure roll 46 having a control bore 51 which passes through the enlarged diameter end portion 52 and small diameter end portion 55. The pressure roll 46 is rotatably supported in the bore 51 by pairs of bearings 53 and 54 which are secured to shaft 56 for rotation therewith. The shaft 56 is eccentrically supported by bushings 58 and 60 for rotation about an eccentric axis A displaced from the common central axis B of the bushings 58 and 60. The bushings 58 and 60 are suitably journaled in the side frames 62 and 64, respectively. With this arrangement, the eccentric relation between the shaft 56 and the bushings 58 and 60 provide for the rotation of the axis A around the axis B.

The pressure roll 46 has a gear 66 secured to the end of the small diameter end portion 55 for rotation therewith. The gear 66 is in meshing relation with a gear 68 secured to the shaft 70 of feed roll 48. The shaft 70 is suitably journaled at one end in the side frame 64, and the other endextends through side frame 62 for axial connection outboard thereof to gear 72. The gear 72, in turn, is connected in meshing relation with gear 74 also positioned on the outboard side of the frame 62. The gear 74 is supported for rotation on shaft 76 journaled at the other end in the side frame 64. A gear 77 is secured to the shaft 76 for rotation therewith and meshes with gear 78 rotatably supported by the shaft 79 which is bolted to the side frame 62. A suitable drive motor (not shown) drivingly connected to gear 78 transmits rotation to the shafts 76, 70 and 56 through the gear train provided by meshing gear pairs 78 and 77, 74 and 72 and 68 and 66 at a preselected speed higher than the speed provided by the envelope machine drive which draws the web material 28 through the pressure rolls 25.

As illustrated in FIGS. 1, 2and 3, a pair of spaced parallel tension arms 80 and 81 are supported on the shaft 56 for rotation therewith and extend substantially vertically upwardly therefrom. A shaft 82 connects the tension arm 80 to the tension arm 81 passing through aligned bores therein. The shaft 82 extends through the axial bore 85 of roll 50 and is nonrotatably supported therein by a pair of bearings 83 and 84 which support the tension sensing roll 50 on the shaft 82 for rotation relative thereto.

A lever arm 86 is nonrotatably supported on the shaft 56 and extends horizontally outwardly therefrom. A crank 87 as illustrated in FIG. 1, having a handle portion 90 and a cylindrical end portion 88 is positioned adjacent the lever arm 86 in underlying relation thereto. By rotation of handle 90, the cylindrical end portion 88 is urged toward and away from the lever arm 86 as indicated by the phantom lines illustrated in FIG. 1. The force exerted upwardly by the crank 87 against the lever arm 86 is transmitted therefrom to the shaft 56 which then rotates on axis A in a counterclockwise direction about axis B. Rotation of shaft 56 moves the pressure roll enlarged diameter portion 52 laterally into and out of frictional engagement with the surface of the web material 28 so that the web 28 is threaded over wraparound roll 44 and engaged in abutting relation with the feed roll 48.

A pair of adjusting bolts 92 and 94 are threadably secured to the envelope machine side frame above and below the lever arm 86. Compression springs 96 and 98 are connected at one end to the adjusting bolts 92 and 94, respectively, and at the other end to the lever arm 86. By adjusting the bolts 92 and 94, the compression in the springs 96 and 98 may be increased or decreased to maintain the lever arm 86 in a substantially horizontal position. By limiting the displacement of lever arm 86 from the horizontal position relative to the shaft 56,

a preselected resistance to rotation about shaft 56 is applied to the tension bars 80 and 81 thereby centering arms 80 and 81 above rolls 46 and 48. In addition, a pair of stop members 100 and 102 are axially supported on the bolts 92 and 94 respectively to maintain the lever arm 86 in a substantially horizontal position.

In operation, the envelope machine drive feeds the web material 28 from the roll 24 at a preselected linear speed required for completion of the envelope forming operations in timed relation to each other. The web material 28 is drawn between the rolls 46 and 48 of the web unwind unit 14 and upwardly therefrom into contact with the tension sensing roll 50. The tension sensing roll 50 is retained in abutting relation with the web material 28 which continuously exerts pressure against the web material 28. Consequently, the tension sensing roll 50, responsive to variations which occur in the tension on the web material fed into and through the envelope machine, pivots about the shaft 56 to thereby maintain a uniform tension in the web material 28.

When the tension on the segment of web material between the rolls 46 and 48 and the pressure rolls 25 increases above the desired tension, the tension sensing roll 50 and tension arms 80 and 81 operably respond to the increase in pressure exerted by the web material 28 upon the roll 50 by rotating in a clockwise direction about shaft 56. The clockwise rotation imparted to shaft 56 by the tension arms 80 and 81 rotates the shaft 56 about the eccentric axis A which, in turn, revolves about axis B. The clockwise rotation of the shaft 56 moves the pressure roll 46 laterally thereby urging the web material 28 into frictional engagement between rolls 48 and 46, as illustrated in FIG. 3. Thus, when feed roll 48 is driven at a speed 1.05 times greater than the speed of the envelope machine drive, the web material 28 is tightly engaged between the nip 49 of rolls 48 and 46 and advances at a feed rate greater than the feed rate provided by the envelope machine drive. Accordingly, an increase in speed of the web material 28 fed to the envelope machine decreases the web tension in the segment between the rolls 46 and 48 and the pressure rolls 25.

The rolls 46 and 48 of the unwind unit 14 continue to feed the web at a greater speed until the tension sensing roll 50 responds to the decrease in pressure exerted by the web material 28 associated with a decrease in web tension by rotating in a counterclockwise direction. Counterclockwise rotation of tension arms and 81 revolves axis A of shaft 56 also in a counterclockwise direction around axis B to thereby move the pressure roll 46 laterally and out of frictional engagement with the web material 28. Once the web material 28 is freed from frictional engagement between the rolls 46 and 48, as illustrated in FIG. 4, the rolls 46 and 48 no longer feed the web material to the pressure rolls 50 at a greater linear speed. The segment of the web material 28 between the unwind unit 14 and the pressure rolls 25 is then drawn by the envelope machine drive at a slower preselected speed. Once the 1.05 overfeed effect is terminated, tension is restored on the web material 28 and the pressure exerted thereby against the tension sensing roll 50 is increased. With the above apparatus, it is now apparent that the tension sensing roll 50 constantly oscillates in a back and forth motion with the tension arms 80 and 81 responding to variations in pressure exerted by the web material 28 as a result of changes in the tension of the web material being fed into the envelope machine. In this manner, a uniform web tension is maintained on the web material 28 being drawn into the envelope machine.

According to the provisions of the patent statutes, I have explained the principle, preferred construction and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, it should be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. Apparatus for controlling the tension on web material comprising,

a roll of web material rotatably supported to permit continuous unwinding of the web material from said roll,

apparatus for further processing the web material in which the web material is arranged to move at a first preselected linear speed,

an unwind means for intermittently feeding the web material at a second preselected linear speed to said apparatus for further processing the web material, said unwind means positioned adjacent said roll of web material so that the web material is supplied to said unwind means,

said second preselected linear speed being higher than said first preselected linear speed,

said unwind means includes a feed roll and a pressure roll positioned adjacent thereto, at least one of said rolls being driven at said second preselected linear speed,

a tension sensing means for sensing the tension in a segment of the web material between said unwind means and said apparatus for further processing the web material,

said tension sensing means positioned adjacent said pressure roll and operably connected thereto for moving the pressure roll toward and away from said feed roll so that said web material is frictionally engaged between said feed roll and said pressure roll so that said web material is fed to said apparatus for further processing the web material at said second preselected linear speed thereby maintaining desired tension in a segment of the web material between said unwind means and said apparatus for further processing the web material.

2. Apparatus for controlling the tension on web material as set forth in claim 1 in which,

said tension sensing means positioned in abutting relation with said web material between said unwind means and-said apparatus for further processing the web material so that said web material continuously exerts an opposing force upon said tension sensing means. i I

3. Apparatus for controlling the tension on web material as set forth in claim 1 in which said tension sensing means includes,

a tension sensing roll having a central bore therethrough and positioned in abutting relation with said web material between said unwind means and said apparatus for further processing the web material so that said web material continuously exerts a predetermined opposing force upon said tension sensing roll,

said tension sensing roll is mechanically connected to said pressure roll for rotational movement about the longitudinal axis of said pressure roll so that upon rotation of said tension sensing roll said. pres.- sure roll moves toward and away from said feed roll.

4. Apparatus for controlling the tension on web ma terial as set forth in claim 1 in which said tension sensing means includes,

a tension sensing roll mechanically connected to said feed roll for rotational movement about the longitudinal axis of said feed roll so that upon rotation of said tension sensing roll said feed roll moves toward and away from said pressure roll.'

5. Apparatus for controlling the tension on web material as set forth in claim 1 which includes,

a pair of bushings nonrotatably mounted in a frame portion adjacent said unwind means and below said tension sensing roll, said bushings coaxially aligned on a common central axis passing therethrough,

a first shaft member rotatably supported by said bushings,

said first shaft member having an axis of rotation in said bushings eccentrically displaced from the common central axis of said bushings so that the axis of rotation of said first shaft member revolves about the common central axis of said bushings upon rotation of said first shaft member,

a second shaft member positioned in the central bore of said tension sensing roll to permit rotation of said tension sensing roll relative to said second shaft member,

a pair of tension arms nonrotatably secured at one end in spaced parallel relation to the ends of said terial as set forth in claim 5 wherein,

said tension sensing roll positioned to continuously apply a predetermined pressure upon said web material and operable to rotate with said tension arms in clockwise and counterclockwise direction for maintaining a predetermined pressure upon said web material as the tension thereon increases and decreases.

7. Apparatus for controlling the tension on web material as set forth in claim 1 in which,

said pressure roll is supported for relative rotation upon said first shaft member and positioned thereon between said pair of tension arms,

said feed roll rotatably supported in said frame portion adjacent said pressure roll and positioned in abutting relation with the web material,

means for rotating said first shaft member to thereby urge said pressure roll into abutting relation with the web material so that the web material is frictionally engaged between said pressure roll and said feed roll.

8. Apparatus for controlling the tension on web material as set forth in claim 1 in which,

said tension sensing roll rotates with said tension arms in clockwise direction about said first shaft member in response to an increase in tension on a .segment of the web material between the unwind means and the apparatus for further processing the web material to thereby urge said pressure roll toward said feed roll into abutting relation with the web material so that the web material is thereby frictionally engaged between the feed roll and the pressure roll and is fed to the apparatus for further processing the web material at said second preselected linear speed.

9. Apparatus for controlling the tension on web material as set forth in claim 1 in which,

said tension sensing roll rotates with said tension arms in counterclockwise direction about said first shaft member in response to a decrease in tension on a segment of the web material between the unwind means and the apparatus for further processing the web material to thereby urge said pressure roll away from said feed roll out of abutting relation with the web material so that the web material is pulled through the apparatus for further processing use web material at said first preselected linear spee 10. Apparatus for controlling the tension on web material as set forth in claim 1 in which,

said second preselected linear speed is higher than said first preselected linear speed by a factor of 1.05.

11. Apparatus for controlling the tension on web material as set forth in claim 1 which includes,

a wraparound roll rotatably supported in said frame portion adjacent said feed roll, said wraparound roll positioned in abutting relation with said web material,

means drivingly connecting said wraparound roll to said feed roll to said pressure roll for transmitting rotation from said wraparound roll to said feed roll so that the web material passing between said feed roll and said pressure roll if fed upwardly therefrom into abutting relation with said tension sensing roll at said second preselected linear speed.

- l k II! l 

1. Apparatus for controlling the tension on web material comprising, a roll of web material rotatably supported to permit continuous unwinding of the web material from said roll, apparatus for further processing the web material in which the web material is arranged to move at a first preselected linear speed, an unwind means for intermittently feeding the web material at a second preselected linear speed to said apparatus for further processing the web material, said unwind means positioned adjacent said roll of web material so that the web material is supplied to said unwind means, said second preselected linear speed being higher than said first preselected linear speed, said unwind means includes a feed roll and a pressure roll positioned adjacent thereto, at least one of said rolls being driven at said second preselected linear speed, a tension sensing means for sensing the tension in a segment of the web material between said unwind means and said apparatus for further processing the web material, said tension sensing means positioned adjacent said pressure roll and operably connected thereto for moving the pressure roll toward and away from said feed roll so that said web material is frictionally engaged between said feed roll and said pressure roll so that said web material is fed to said apparatus for further processing the web material at said second preselected linear speed thereby maintaining desired tension in a segment of the web material between said unwind means and said apparatus for further processing the web material.
 2. Apparatus for controlling the tension on web material as set forth in claim 1 in which, said tension sensing means positioned in abutting relation with said web material between said unwind means and said apparatus for further processing the web material so that said web material continuously exerts an opposing force upon said tension sensing means.
 3. Apparatus for controlling the tension on web material as set forth in claim 1 in which said tension sensing means includes, a tension sensing roll having a central bore therethrough and positioned in abutting relation with said web material between said unwind means and said apparatus for further processing the web material so that said web material continuously exerts a predetermined opposing force upon said tension sensing roll, said tension sensing roll is mechanically connected to said pressure roll for rotational movement about The longitudinal axis of said pressure roll so that upon rotation of said tension sensing roll said pressure roll moves toward and away from said feed roll.
 4. Apparatus for controlling the tension on web material as set forth in claim 1 in which said tension sensing means includes, a tension sensing roll mechanically connected to said feed roll for rotational movement about the longitudinal axis of said feed roll so that upon rotation of said tension sensing roll said feed roll moves toward and away from said pressure roll.
 5. Apparatus for controlling the tension on web material as set forth in claim 1 which includes, a pair of bushings nonrotatably mounted in a frame portion adjacent said unwind means and below said tension sensing roll, said bushings coaxially aligned on a common central axis passing therethrough, a first shaft member rotatably supported by said bushings, said first shaft member having an axis of rotation in said bushings eccentrically displaced from the common central axis of said bushings so that the axis of rotation of said first shaft member revolves about the common central axis of said bushings upon rotation of said first shaft member, a second shaft member positioned in the central bore of said tension sensing roll to permit rotation of said tension sensing roll relative to said second shaft member, a pair of tension arms nonrotatably secured at one end in spaced parallel relation to the ends of said second shaft member and extending substantially vertically downwardly therefrom for connection at said tension arms other end to the ends of said first shaft member for rotation therewith.
 6. Apparatus for controlling the tension on web material as set forth in claim 5 wherein, said tension sensing roll positioned to continuously apply a predetermined pressure upon said web material and operable to rotate with said tension arms in clockwise and counterclockwise direction for maintaining a predetermined pressure upon said web material as the tension thereon increases and decreases.
 7. Apparatus for controlling the tension on web material as set forth in claim 1 in which, said pressure roll is supported for relative rotation upon said first shaft member and positioned thereon between said pair of tension arms, said feed roll rotatably supported in said frame portion adjacent said pressure roll and positioned in abutting relation with the web material, means for rotating said first shaft member to thereby urge said pressure roll into abutting relation with the web material so that the web material is frictionally engaged between said pressure roll and said feed roll.
 8. Apparatus for controlling the tension on web material as set forth in claim 1 in which, said tension sensing roll rotates with said tension arms in clockwise direction about said first shaft member in response to an increase in tension on a segment of the web material between the unwind means and the apparatus for further processing the web material to thereby urge said pressure roll toward said feed roll into abutting relation with the web material so that the web material is thereby frictionally engaged between the feed roll and the pressure roll and is fed to the apparatus for further processing the web material at said second preselected linear speed.
 9. Apparatus for controlling the tension on web material as set forth in claim 1 in which, said tension sensing roll rotates with said tension arms in counterclockwise direction about said first shaft member in response to a decrease in tension on a segment of the web material between the unwind means and the apparatus for further processing the web material to thereby urge said pressure roll away from said feed roll out of abutting relation with the web material so that the web material is pulled through the apparatus for further processing the web material at said first preselected linear speed.
 10. Apparatus for controlling the tension on web materIal as set forth in claim 1 in which, said second preselected linear speed is higher than said first preselected linear speed by a factor of 1.05.
 11. Apparatus for controlling the tension on web material as set forth in claim 1 which includes, a wraparound roll rotatably supported in said frame portion adjacent said feed roll, said wraparound roll positioned in abutting relation with said web material, means drivingly connecting said wraparound roll to said feed roll to said pressure roll for transmitting rotation from said wraparound roll to said feed roll so that the web material passing between said feed roll and said pressure roll if fed upwardly therefrom into abutting relation with said tension sensing roll at said second preselected linear speed. 